if the feature is just missing, you might just want to deploy/install it again.

- which scope was the feature?
- when did the feature disappear? After a solution was retracted? After the content database was migrated? ...

Sometimes, when a feature is uninstalled from the farm, it does not automatically leave faulty left overs. If there is nothing to clean up from the feature, the feature admin will not find any faulty feature.

If you are trying to reactivate a deactivated feature, you should select the site, where you want to activate the feature and then go to the list of installed features in the farm within the feature admin. There, select the feature to be activated and click
the button below, where you want to activate the feature.

The Faulty Feature checks for orphaned parts of features in feature collections. Usually, the feature definition was removed without deactivating all features everywhere in the farm before that.

You might have a different problem: Maybe you have just a faulty feature definition.
In this case, just go to the feature definition tab and scroll down the features (after hitting "Load").
If it says "Error", you found a faulty feature definition, that you just could uninstall with the feature admin.

If you want to search for the term "error" automatically instead of scrolling down, you can select the messages in the log, copy them in your favorite editor and then search for "error".